Blog by John Stewart: Can a Four Runway Heathrow Really be Quieter?

In an interesting and detailed blog, John Stewart (Chair of HACAN) sets out what the effect will be of having a 4 runway Heathrow, as proposed by the Policy Exchange last year. Their plan is for 4 runways parallel, some 3.9 kilometres further west than the current runways, all of which could work at once. And they claim this will cause less aircraft noise for Londoners. John assesses this claim, and finds that  the plan envisages up to 960,000 planes per year (cf. 480,000 now) and there would be no rest periods for Londoners during the day. Though the plan is for there to be no night flights, and for smaller planes to come in to land over London at higher altitudes due to a steeper glideslope, there is not likely to be an improvement in the noise experienced. Though smaller planes may be able to come in at a 5 degree glideslope, the noisier planes will have to continue on a 3 degree approach. What thousands of Londoners want is runway alternation and respite periods. They will not get these from the Policy Exchange proposal.



Can a Four Runway Heathrow Really be Quieter?

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Blog by John Stewart

When the Policy Exchange published a report (1) at the end of last year calling for a new four runway airport to be built a few miles west of the existing Heathrow, it wasn’t taken too seriously.  It was seen as just another report coming up with yet another idea for a new airport.  However, it has emerged in the last few weeks that the Department for Transport – and possibly also the Airports Commission, under Sir Howard Davies – is beginning to take it seriously.

The plan envisages an airport with a capacity of 960,000 planes (up from 480,000 today) and an end to runway alternation but Tim Leunig, the smart and engaging author of the report, says its proposals can “build a cost-effective hub airport that works for passengers, airlines and those who live nearby.”

It is a big claim.  And the part that seems particularly to interest the authorities is its claim that the new airport will “significantly reduce noise over West London.”  They believe that noise is the biggest barrier to Heathrow expansion.  A view shared by Heathrow Airport (formerly BAA) though they have not endorsed the report and indeed they argue that only one more runway is required.

.Proposed four runway Heathrow from Policy Exchange's 'Bigger and Quieter' report

Policy Exchange map of their proposals


What is being proposed

The plan is for a four runway airport:

“the runways would be 3km long, grouped as two close coupled pairs, aligned east-west, and located immediately to the west of the current airport.  The existing runways would cease to operate as runways.  The new runways would extend across the M25.”

 The two outer runways would be for landings.  The two inner runways for take-offs.  The most northerly runway would be level with the current northern runway, with the most southerly approximately 300, south of the current southern runway. All runways would operate at the same time throughout the day.

“The airport would have twice the capacity of the current Heathrow, implying a maximum of around 960,000 movements and 140m passengers [but] a sensible working maximum would be 850,000 movements and 121m passengers”.

 There would be three terminal buildings, situated between the two pairs of runways: Terminal 5, Terminals 1,2 and3, and a new terminal replacing Terminal 4.There are plans to improve public transport to the new airport.


What about the claim that noise levels will be reduced?

 The plan is this:

  • There would be no night flights.
  • The noisiest planes would be banned from Heathrow.  Planes like the 747 would be banned: “this is not possible in the short run, but could be achieved by 2030, a plausible date for this airport to open.”
  • A steeper descent approach would be introduced for the smaller planes using the airport but that would not be possible for the larger planes.
  • The very fact that the runways would be 3.9km west of the existing airport means that the planes would be higher over West London.

The report claims:

“The effect of moving the runway 3.9km to the west, combined with a steeper rate of descent means that the planes will be radically higher over any given place in London.”

 This would mean:

“Narrow bodied planes will be 925m, rather 260m above Hounslow.  This is the height of planes above Wandsworth at present.  The same is true for Richmond, where the height of the narrow bodied planes would rise from 500m to 1400m, the current height when flying over Peckham.”

 The improvement is much less dramatic for the larger planes:

“We assume that wide bodied planes will continue to land at 3 degrees.  There is still an improvement over West London, however, because the runways have moved about 4km west.  This means that a wide bodied plane over Hounslow would be akin to one currently over Richmond, Richmond would be akin to one currently over Barnes…..”

 The plan would be to land the smaller planes on the northern runway for one week and switch to the southern runway for the next week.

The report argues that moving the runways west “also helps West London when take-offs are towards the east………no one will be directly underneath the plane for its first 5 kilometres of ascent.”


What of people west of the airport?

“Since wide-bodied planes will land on their current angle of descent, but land 3km further west, they will be lower above any given place on their descent.  Against that, the noisiest planes have been eliminated, so the effect on the total noise is ambiguous.  More planes will be noticeable, but fewer planes will be exceptionally loud…. the position is different for narrow bodied planes since they will be descending at a steeper angle. 

 “Places between Datchet and Heathrow will have lower aircraft, while places west of Datchet will experience less noise” 

“Far more people live west of the proposed northern runway than west of the proposed southern runway.  For that reason, narrow bodied easterly arrivals would always land on the northern runway.”


HACAN’S Assessment

Individual planes over many areas would be quieter.  There are, however, three very big ‘buts’.

  • The total number of planes would rise to at least 850,000 a year, and maybe even close to 960,000 – up from around 480,000 at present.  That is at least another 1,000 planes a day using the airport.
  • It would be all-day flying.  There would be no break from the constant noise.
  • There is nothing in the proposals about the impact on areas further from Heathrow.  Presumably the report assumes that the higher, quieter planes would not pose a problem.  But what many of these areas would face would be constant all-day flying.

Over the past 15 years three of the top concerns from people under the flight paths have been (the other one has been night flights):

  •  The steady increase in flight numbers
  • The desire to retain runway alternation
  • The demand from people further from the airport for respite periods.

None of these are addressed in this Policy Exchange Report.  For all its interesting ideas for cutting noise, London and much of the Home Counties would remain under a sky of sound.


(1). The Policy Exchange report can be found at:


 HACAN blog at



HACAN ClearSkies is the largest voluntary organisation in Europe dedicated to campaign on behalf of those who suffer because of aircraft flight paths. 

HACAN = Heathrow Association for the Control of Aircraft Noise